Spark plug



mmm

I WITNESS:

III-Ilium F. L. BRONSON.

SPARK PLUG.

APPLICATION FILED MAR. 5. I921.

fidL.Brqnsan Patented Oct. 24,1922.

/f3 I l I I I I I I 1 1l\ I J l INVENTOI ATTORNEY Patented Oct; 24,1922. V

UNITED STATES PATENT OFFICE.

FRED L. BRONSON, OF WIGHITA FALLS, TEXAS. ASSIGNOR 0F ONE-FIFTH TO HARRIS ALEXANDER, ONE-FIFTH T0 ARTHUR B. JOHNSTON, ONE- FIFTH TO HOWARD EARL JOHNSTON, AND ONE'FIFTH .TO ANDY J. ALEXANDER, ALL OF WICHITA' FALLS,

TEXAS.

SPARK PLUG.

Application filed March 5, 1921.

To aZZ w/mm it may concern.

Be it known that I, Fran L. Bnonson, a citizen of the United States, residing at Wichita Falls, in the county of \Vichita and State of Texas, have invented new and useful Improvements in Spark Plugs, of which the following is a specification.

One object of my present invention is the provision of a spark plug of simple'and inexpensive construction, characterized by efiicient exterior and interior insulation, and the capacity to afford an intense spark due to the effective prevention of leakage of current through any path other than that including the main and ground electrodes.

Another object of the invention is the provision of a spark plug in which provision is made to preclude fouling of the plug in carbon.

To the attainment of the foregoing, the invention consists in the improvements as hereinafter described and definitely claimed.

In the accompanying drawings, forming part hereof:

Figure 1 is an elevation of the spark plug constituting the best practical embodiment of my invention that I have as yet devised; the said plug being especially, though. not necessarily, designed for use in aeroplane motors for reasons hereinafter set forth.

Figure 2 is a diametrical section of the lug. p Figure 3 is an inverted plan of the plug.

Figure 4 is a transverse section taken in the plane indicated by the line 4-4 of Figure 2.

Similar numerals of reference designate corresponding parts in allof the views of the drawing...

Among other elements my novel spark plug comprises a body 1, threaded at 2 for connection to a motor cylinder and provided with a longitudinal central bore 3, and a chamber 4; the said chamber 4 being in communication with the bore 3 and bein located in the inner end portion of the boy 1 and partly defined by an annular flange 5 at the inner end of the said body. The plug also comprses a ground electrode 6 carried at 7 by the body 1 and having its terminal 8 located in the longitudinal center of the plug. For cooperation with the ground electrode 6 the plug includes a main electrode 9 adapted to be connected at its upper Serial No. 449,923.

end in any approved manner with a wire leading from a source of electric energv, though I prefer to provide for the purpose a nut 10 anda cap nut 11, threaded on the upper end portion of said electrode. Surrounding the main electrode 9 and arranged immediately below the nut 10 is a flanged cap plate 12 which may be of metal or any other appropriate material. Occupying the bore 3 of the body 1 and extending down into the chamber 4 and upwardly beyond the body 1 is a dielectric or insulating tube 13. The said tube 13 is preferably formed of a sheet of mica wound laterally about the main electrode 9. Superimposed on the body 1 and surrounding the tube 13 is an insulating annulus 14. preferably of mica. This annulus 14 may be in one unit or may be composed of a plurality of superimposed disks, in the discretion. of the manufacturer and without involving departure from the scope of my invention. Immediatelyabove the insulating annulus 14 is an insulating annulus 15 also preferably of mica and adapted to be formed in one unit as illustrated or of a plurality of superimposed units or disks as desired. The annulus 15 is of larger diameter than the annulus 14 in about the proportion illustrated to afford an overhanging portion above the annulus 14 and the metallic body 1, and is characterized by sharp square corners 16 for an important purpose hereinafter set forth. Surrounding the upper portion of the tube 13 and the main electrode 9 and interposed between the annulus 16 and the cap plate 12 is an insulating cap member 17 of mica or other appropriate material. This capmember 17 may be in one unit as shown or may be formed of'a plurality. of superimposed sections as is found most desirable.

It will be apparent from the foregoing that the annulus 16 constitutes an eflicient guard flange having the capacity in combination with the lower and upper insulating members 14 and 17, to prevent dissipation of current exterior-1y of the plug between the 

